what is the issue exactly?
Using demo project you can select text then tap on "HL" option to highlight.
If you need to customize this feature, you can take a look at OnLongPressed method in RDPDFViewController class (enable the text selection mode), to better understand how text selection and highlight works.
Here is a quick explanation of markup annotations:
vSelMarkup method has 2 parameters: color and type.
- Color parameter allows you to set annotation color, in this case you can set it dynamically to have different colours.
- Type parameter is used to set the annotation type:
3: Highlight without round corner
4: Squiggly underline.
In demo project you can choose which type of annotation apply to selected text using the choice menu.
You can modify this behaviour to satisfy your needs, for example you can call the highlight in OnSelEnd method of RDPDFViewController to skip the choice menu.